Rubber product and composition



1 UNITED STATES PATENT OFFICE.

JOHN M, WEISS, OF NEW YORK, N. Y., ASSIGNOR TO THE BARRETT COMPANY, A CORPORATION OF NEW JERSEY.

RUBBER. rnonncr AND comrosrrroni Io Drawing.

and compositions, and more particularly-to solutions containing products and compositions of improved di-electric pro'perties having incorporatedtherewith, prior to the vulcanization, a semi-solid to solid bitumen obtainable by the destructive distillation of coal tar and coal tar pitch. The invention also relates to fabrics and other porous and non-porous substances saturated, impregnated or. coated with such solutions.

:In the destructive distillation of coal tar and of coal tar pitch, there is obtained, at the final stage of evolution of condensible distillate, a semi-solid to solid product of characteristic composition and properties. This product is bituminous in character and -may properly be referred to as a bitumen. within the standard definition of the American Society for Testing Materialsf This bitumen is an extremely high boiling product and undergoes partial decomposition if distilled under atmospheric pressures. It varies in color from a dark brown to a clear cherry red product, and can readily be obtained in the form of a light colored product relatively freefrom black or brown coloration and free from free carbon. It is very resistant to dilute acids and alkalis, and it is soluble in such common solvents as benzol, and coal tar naphthas, etc.

This semi-solid to solid bitumen, thus obtainable by the destructive distillation of coal tar and coal tar pitch, may be melted by the application of heat, and may have a melting point varying, for example, from around 110 to 115 F. or lower, up to around 145 to 155 F., or even as high as 190 F. or higher, the melting point being determined according to the cube melting point method for bituminous materials described by S. R. Church in the Journal of Industrial and Engineering Chemistry for April, 1911. The specific gravity of the bitumen is unusually high,- -certain samples thereof, which have been examined, showing specific gravities, at about l5.5.C., from components.

Specification of Letters Patent. 7 Patented Mar. 16, 1920. Application filed July 3. 1919. Serial No. 308,509. I.

around 1.233 or even lower up to around 1.25 or higher.

The bitumen moreover has remarkable dielectric properties. Samples of the bitumen have been found to have as high a di-electric strength as 550 to 700 volts per mil. or even igher.

This bitumen, with its characteristic composition and properties, is obtainable from coal tar or coal tar pitch by differentmethods of procedure. It may thus be ob-- tained as the last fraction of the condensable distillatein the straight distillation of coal tar to coke, this last fraction being properly cut so that the bitumen is substantially free from greases and lower boiling Again, where the distillation of the coal tar has proceeded only to the formation of coal tar pitch, this pitch may be subjected to a redistillation, for example, in a coke oven, and the bitumen obtained therefrom at the end of the destructive distillation, and at the final stage of evolution of condensable distillate as above described.

The fractions of the distillate which come over before the semi-solid and solid bitumen frequently carry with them appreciable amounts of the bitumen, and the bitumen. may be obtained from these distillates by a suitable redistillation.

It will be evident that various specific methods of procedure may be followed, and that different types of apparatus may be used, in the production of the bitumen by the destructive distillation of the coal tar or coal tar pitch.

The bituminous substance or bitumen thus obtainable will be hereinafter referred to, in the specification and in the appended claims, simply as the bitumen, or as the semisolid to solid bitumen obtainable by the destructive distillation of coal tar pitch.

Wherethe bitumen is initially produced in an impure state it may be further purified, by distillation or otherwise, for example, by steam or vacuum distillation. If distilled under ordinary pressures the bitumen undergoes partial decomposition, forming greasy bodies, some apparently unchanged bitumen and coke residue, so that such distillation will not generally be feasible for purification of the impure bitumen; but the composition and consistency of the bitumen may nevertheless be modified by careful distillation, and particularly under a suliicient vacuum to lower materially the temperature of distillation.

According to the present invention, the semi-solid to solid bitumen above referred to is incorporated with the rubber and other constituents of the rubber products or compositions to be vulcanized, so that the bitumen is present durin the vulcanization with corresponding modification of the vulcanization process, and withthe production of a correspondingly modified vulcanized product.

The properties of the bitumen above referred to, such as its resistance to alkalis and acids, its high specific gravity, and its unusual (ii-electric properties, inhere to a greater or less extent, in the vulcanized products in the production of which the bitumen is employed. The vulcanized products will thus be of increased density due to the high specific gravity of the bitumen itself, while the di-electric properties of the rubber compositions and products will be similarly benefitted by the incorporation .of the bitumen therein.

The compositions'and products of the present invention are of especial value for purposes where a light colored product is desired. It is well known that coal tar pitch, and the usual asphaltic and bituminous components of rubber mixtures, are of a black color, and correspondingly darken the vulcanized products in the production of which they are employed. The bitumen employed in the process of the present invention, however, when properly prepared and purified, is substantially free from objectionable black coloration, and has a pleasing clear and usually cherry red coloration. which imparts to the compositions and products, in the manufacture of which the bitumen is employed a slight but unobjection-able tint. Such vulcanized products and compositions, accordingly, may be used where light colored rubber products are de- .sire(l and where black products would be undesirable. The advantage of lightness in color, as will be evident, will be an added advantage, in addition to the other desirable properties imparted to the vulcanized products by the bitumen.

The bitumen may, however, be used to advantage in the production of compositions or products where light color is not'of importance, and where it may even be desirable to produce a dark or black product. In such cases the other advantages of the bitumen will be retained. bitumen itself need not be entirely free from dark coloration, but may even have a pronounced dark brown color, although. as above "pointed out, it can readily be produced substantially free from objectionable dark coloration.

In. the production of high grade rubber For such purposes, the

products and compositions, the higher grades of rubbers, such as Para or plantation rubbers, will usually be employed. For other purposes, other rubbers of an inferior grade may be employed. In any case, the composition or mix may contain fillers of various kinds, or pigments, or other specific substances or reagents, such as, for example, zinc oxid, lithopone, etc., for hardening the rubber or imparting special properties to the resulting final composition or product. The vulcanization process can be carried out by the incorporation of an appropriate amount of sulfur either with or without other agents for promoting or modifying the vulcanization process. For hard rubber products more sulfur will be employed than for soft rubber products. The amount of the vulcanizing agent, as Well as the time, temperature and pressure of vulcanization, will vary with the nature of the composition and with the character of the product which it is desired to produce, 6. 9., Whether the product is to be a soft vulcanized product or a hard rubber product.

The bitumen may be incorporated with the other rubber constituents with advantage bythe use of solutions of the bitumen and by uniform distribution of such solutions throughout the rubber, or by the use of solutions of the bitumen in solvents which are likewise solvents of the rubber it self. This will be of especial advantage in the production of so-called solutions of rubber such as are used for waterproofing fabrics and the like, since the bitumen and the rubber may be dissolved in common solvents and a uniform distribution of the bitumen and rubber thereby promoted. Where such rubber solutions are made and used, the solvent may be subsequently removed, leaving the bitumen intimately combined with the rubber and other constituents of the rubber composition, and the vulcanization may be then effected in any suitable manner, as by the so-called cold vulcanization process, making use of sulfur chlorid, or by the Wellknown hot room process, or otherwise.

It will be understood that so-called waste or reclaimed rubber may be employed .in the production of the compositions and-prod acts of the present invention, for example, i in admixture with the higher grades of rub-' her. and the waste or regenerated rubber will be modified by the vulcanization thereof, in admixture with the itumen.

Vulcanized. products may be similarly prepared by the use of able oils, which, upon vulcanization, produce so-called rubber substitutes. The hereinbefore described bitumen may, with similar advantages to those above referred to, be incorporated in such compositions, prior to their vulcanization. It will be evident also that vulcanizable oils may be incorporated so-called vulcanizwith rubber in the preparation of composite vulcanized products in the production of which the bitumen is also utilized.

The invention will be further illustratedby the following specific examples of com positions made in accordance therewlth.

Such mixtures may be subjected to vulcanization. for example, tor a period of.

thirty minutes at a steam pressure of fortyfive pounds; but the time and pressure (and corresponding temperature) may vary within rat-her widejlimits, depending upon the particular use for which the product is desired.

\Vhere hard rubber products are desired, a much larger percentage of sulfur will be used and the vulcanization process will be correspondingly modified. So also. various fillers or compounding materials may be used. depending upon the purposes for which the resulting products are desired.

The products thus produced will be of improved density and di-electric properties due to the hcreinbet'ore described bitumen employed in their production. \Vhere the bitumen of cherry red color the products will be light colored products. substantially free from dark coloration, if the rubber and other ingredients employed are themselves tree from dark coloration. At the same time, the products or compositions will have the other characteristic properties imparted to them by the bitumen. inasmuch as the bitumen is free from dark coloration it will likewise be free from tree carbon, which, if-

by the addition of various pigments and coloring materials, without the disadvantages incident to the use of black ingredients such as coal tar pitch and the like, or carbonaceous components of an essentially black character.

The amount of the hereinbeto-re described bitumen which may be used, in the production of the improved compositions and products of the present invention, may vary within rather wide limits, as Will be evident from the specific examples above given, and depending on such considerations as the nature of the mix, the components of which the mix is made up, the object for which the product is desired, and the nature of the vulcanization process, whether hot. or cold, and whether for the production of hard or soft rubber products.

While the invention has been more par tic ularly described in connection with vulcanized compositions and products, yet it will be understood that unvulcanized compositions and products may be similarly produced by the incorporation therein of the bitumen, and that these compositions may be-employed ivit-hout vulcanization or for purposes where vulcanization is to be subsequently effected, for example, in the coating of fabric where the coating Is to be subsequently vulcanized.

Claims: 1. As new compositions of matter, solutions'containing, in a common solvent, rubber and a semi-solid to solid bitumen obtainable by the destructive distillation of coal tar pitch; substantially as described.

2. As newcompositions of matter, solutions containing, in a common solvent, rubber and a semi-solid to solid bitumen ob tainable by the destructive distillation of coal tar pitch, said, rubber being in excess of said bitumen; substantially as described.

3. As new compositions of matter, solutions containing, in a common solvent, more than of rubber and from about ten to thirty per cent. of a semi-solid to solid bitumen obtainable by the destructive distillation of coal tar pitch substantially as described. v

In testimony whereof I attix my signature.

JOHN M. WEISS. 

